Abnormal fatty acid metabolism in peripheral nerves of patients with pernicious anemia.

Fatty acid synthesis from radiopropionate was evaluated in sural nerve biopsy slices from five normal controls and nine patients with pernicious anemia. The nerves were incubated in [(14)C]propionate, the lipids were extracted, and the fatty acid methyl esters were chromatographed by gas-liquid chromatography. In the normal nerves the radiolabel was found primarily in short chain (C12 and C14) fatty acids. The nerves from pernicious anemia patients showed two fatty acids peaks that were not discernible in the normal nerves, and these fatty acids had retention times intermediate to those of myristic (C14.0) and palmitic (C16.0) acids and palmitoleic (C16.1) and stearic (C18.0) acids, respectively. These two peaks (a C15 and C17 fatty acid) contained the bulk of the radioactivity recovered in the fatty acid fraction after incubation with [(14)C]propionate. Catalytic reduction and rechromatography failed to alter the retention time of these compounds suggesting that they are not unsaturated fatty acids. The nerves from the pernicious anemia patients had a decrease in the mean content of normal fatty acids when compared with the nerves from control patients as well as a decrease in the mean synthesis of normal fatty acids as estimated by isotope incorporation after incubation with [(14)C]propionate or (3)H(2)O. Analysis of myelin isolated from the nerves indicated that the changes at least in part were in that fraction.

The control of iron absorption by the gastrointestinal mucosal cell.

Gastrointestinal mucosal factors controlling rates of iron absorption were studied utilizing an in vivo closed duodenal loop technique. Cellular distribution of newly absorbed radioiron was identified by molecular sieve and iron-exchange chromatography of the mucosal cell supernate. In the normal animal, iron rapidly appeared in ferritin, and this fraction accounted for greater than 90% of mucosal supernatant radioactivity after 60 min absorption time. The nonferritin radioiron appeared to be unbound iron salts. In the presence of increased iron absorption induced by iron depletion or hemolysis, the major difference from the normal distribution pattern was an increase in the proportion and quantity of the free iron salts. Incorporation of newly absorbed iron into ferritin did not correlate with the rate of iron absorption. No evidence was found for a specific soluble iron-chelating molecule within the mucosal cell. The nonheme iron content of the mucosal supernates from iron-deficient and hemolyzing animals were significantly lower than in the normal animal.The data are consistent with hypotheses which suggest that iron absorption rates may be controlled in part by the rate of initial iron uptake by the mucosal cell and that a membrane transport mechanism exists which is modulated by the nonheme iron content of the mucosal cell or some portion thereof.

Osmotic blood-brain barrier disruption. Computerized tomographic monitoring of chemotherapeutic agent delivery.

The present study describes a canine model of transient reversible blood-brain barrier disruption with hyperosmolar mannitol infusion into the internal carotid artery. Studies in this model show that osmotic blood-brain barrier disruption before intracarotid infusion of methotrexate results in markedly elevated (therapeutic) levels of drug in the ipsilateral cerebral hemisphere. Levels in the cerebrospinal fluid correlate poorly and inconsistently with brain levels. Computerized tomograms in this canine model provide a noninvasive monitor of the degree, time-course, and localization of osmotic blood-brain barrier disruption.

Heterogeneity of the molecular lesions in inherited phosphofructokinase deficiency.

Human phosphofructokinase (PFK; EC 2.7.1.11) exists in tetrameric isozymic forms. Muscle and liver contain the homotetramers M4 and L4, whereas erythrocytes contain five isozymes composed of M (muscle) and L (liver) subunits, i.e., M4, M3L, M2L2, ML3, and L4. Inherited defects of erythrocyte PFK are usually partial and are described in association with heterogeneous clinical syndromes. To define the molecular basis and pathogenesis of this enzymopathy, we investigated four unrelated individuals manifesting myopathy and hemolysis (glycogenosis type VII), isolated hemolysis, or no symptoms at all. The three symptomatic patients showed high-normal hemoglobin levels, despite hemolysis and early-onset hyperuricemia. They showed total lack of muscle-type PFK and suffered from exertional myopathy of varying severity. In the erythrocytes, a metabolic crossover was evident at the PFK step: the levels of hexose monophosphates were elevated and those of 2,3-diphosphoglycerate (2,3-DPG) were depressed, causing strikingly increased hemoglobin-oxygen affinity. In all cases, the residual erythrocyte PFK consisted exclusively of L4 isozyme, indicating homozygosity for the deficiency of the catalytically active M subunit. However, presence of immunoreactive M subunit was shown in cultured fibroblasts by indirect immunofluorescence with monoclonal anti-M antibody. The fourth individual was completely asymptomatic, had normal erythrocyte metabolism, and had no evidence of hemolysis. His residual erythrocyte PFK showed a striking decrease of the L4, ML3, and M2L2 isozymes, secondary to a mutant unstable L subunit. Identical alterations of erythrocyte PFK were found in his asymptomatic son, indicating heterozygosity for the mutant unstable L subunit in this kindred. These studies show that, except for the varying severity of the myopathic symptoms, glycogenosis type VII has highly uniform clinical and biochemical features and results from homozygosity for mutant inactive M subunit(s). The absence of anemia despite hemolysis may be explained by the low 2,3-DPG levels. The hyperuricemia may result from hyperactivity of the hexose monophosphate shunt. In contrast, the clinically silent carrier state results from heterozygosity for mutant M or L subunit. Of the two, the M subunit appears to be more critical for adequate glycolytic flux in the erythrocyte, since its absence is correlated with hemolysis.

Adenosine triphosphate-dependent transport of doxorubicin, daunomycin, and vinblastine in human tissues by a mechanism distinct from the P-glycoprotein.

Previous studies have demonstrated that a human glutathione conjugate transporter, designated as dinitrophenyl-S-glutathione ATPase (DNP-SG ATPase), catalyzed ATP hydrolysis in the presence of several amphiphilic compounds other than glutathione conjugates (Singhal, S. S., R. Sharma, S. Gupta, H. Ahmad, P. Zimniak, A. Radominska, R. Lester, and Y. C. Awasthi. 1991. FEBS [Fed. Eur. Biochem. Soc.] Lett. 281:255-257). We now demonstrate that DNP-SG ATPase purified from human lung and erythrocyte membranes catalyzed the hydrolysis of ATP in the presence of doxorubicin and its metabolites. Doxorubicin-stimulated ATP hydrolysis by DNP-SG ATPase was saturable with respect to doxorubicin (Km 1.2 and 2.8 microM for the lung and erythrocyte enzymes, respectively). Antibodies against DNP-SG ATPase immunoprecipitated the ATP hydrolyzing activity stimulated by doxorubicin, its metabolites, and glutathione conjugates. Inside our vesicles prepared from erythrocyte membranes took up doxorubicin, daunomycin, and vinblastine in an ATP-dependent manner. The uptake was linear with respect to time and vesicle protein, was dependent on ATP and magnesium, was inhibited by heavy metal salts or by heating the vesicles, and was sensitive to both osmolarity and orientation of the vesicles. The transport had an activation energy of 13 kcal/mol, was saturable with respect to both doxorubicin and ATP (Km values of 1.8 microM and 1.9 mM, respectively), and was competitively inhibited by glutathione conjugates as well as by a number of amphiphiles such as daunomycin or vinblastine. Transport was diminished upon coating the vesicles with antibodies against DNP-SG ATPase. Incorporation of increasing amounts of purified DNP-SG ATPase into the vesicles resulted in a linear increase in transport of doxorubicin. These studies demonstrated for the first time that a membrane protein that catalyzed the transport of anionic amphiphilic molecules such as glutathione conjugates could also mediate the transport of weakly cationic antitumor antibiotic, doxorubicin. Notably, the Km of transport was in the range of doxorubicin concentration achievable in human serum after intravenous dosing of doxorubicin.

Spontaneous fibrinolysis in pulmonary embolism.

This study correlated levels of activated fibrinolysis with the presence, extent, and rate of resolution of angiographically documented pulmonary emboli. Pulmonary emboli demonstrable by angiography were associated with detectable fibrin split products in the serum of 24 of 25 patients. In the absence of increased fibrin split products, pulmonary emboli large enough to be demonstrated by angiography were found in only 2 of 25 positive pulmonary angiograms. Spontaneous resolution of pulmonary emboli could not be correlated with the the concentration or persistence of fibrin split products but did correlate well with the presence of a reversible precipitating cause. Thrombophlebitis in the absence of clinical evidence of pulmonary embolism was not associated with increased concentrations of fibrin split products in eight of nine patients. The one patient with increased fibrin split product concentration had evidence on lung scan of silent pulmonary embolism.

Characterization of human neuroblastoma cell lines established before and after therapy.

Six new cell lines have been established from human neuroblastomas. Cell line SMS-KAN, from primary tumor before therapy, and line SMS-KANR, from bone marrow after chemotherapy and radiotherapy, were established from the same patient. Cell lines SMS-KCN (from primary tumor before any therapy) and SMS-KCNR (from bone marrow after chemotherapy) were established from another patient. Two other lines (SMS-MSN and SMS-SAN) were established from different patients before any therapy was given. Cell lines established from recurrent disease after chemotherapy (SMS-KANR and SMS-KCNR) had significantly shorter doubling times and increased plating efficiencies compared to those of cell lines derived from the same patient before chemotherapy (SMS-KAN and SMS-KCN). All cell lines contained tyrosine hydroxylase, aromatic L-amino acid decarboxylase, and dopamine-beta-hydroxylase. Measurable amounts of choline acetyltransferase were also detected in SMS-KAN and SMS-KANR. Karyotype analysis showed all cell lines except SMS-MSN to be pseudodiploid with modal numbers of 46 and deletions of the short arm of chromosome 1; SMS-MSN had a modal number of 57-58 chromosomes. All cell lines had double-minute chromosomes, except SMS-KANR, which had abnormally banding regions. These new cell lines provide in vitro models of neuroblastoma suitable for the study of differences in neuroblastoma cell populations before chemotherapy as compared to the cell populations that proliferate after therapy.

Pharmacology and neurotoxicity of cis-diamminedichloroplatinum, bleomycin, 5-fluorouracil, and cyclophosphamide administration following osmotic blood-brain barrier modification.

cis-Platinum, bleomycin, 5-fluorouracil, and cyclophosphamide were administered to rodent and canine models of osmotic blood-brain barrier modification to evaluate the relationship between tissue drug concentration in brain and the physiological and neuropathological effects of the drug. The toxicity studies were carried out in the canine, and the pharmacological studies were carried out in the rodent. Even without the osmotic procedure, intracarotid cis-platinum, in contrast to the other drugs, produced modification of the blood-brain barrier with resultant severe neurotoxicity. Osmotic blood-brain barrier modification was used to increase delivery of bleomycin and 5-fluorouracil to the ipsilateral brain region, but the increased delivery was associated with evident neurotoxicity. Cyclophosphamide administration in association with osmotic blood-brain barrier opening did not cause significant neural toxicity. These studies indicate that some chemotherapeutic agents given in association with osmotic blood-brain barrier opening can result in neurotoxicity. The corollary of the known limited neurotoxicity when these chemotherapeutic agents are used in a conventional manner appears to be due to the presence of the blood-brain barrier.

Selective toxicity of 6-hydroxydopamine and ascorbate for human neuroblastoma in vitro: a model for clearing marrow prior to autologous transplant.

6-Hydroxydopamine (6-OHDA) is a neurotoxin for catecholaminergic neurons and neuroblasts. Since frequent marrow involvement in neuroblastoma restricts the exploitation of stored autologous bone marrow for rescue postchemotherapy, the potential for tumor-specific in vitro specificity of 6-OHDA was studied. The cytotoxic effect of 6-OHDA on 12 human neuroblastoma cell lines was compared to the effect on nonneuroblastoma cell lines. Most neuroblastoma cell lines were very sensitive to 6-OHDA (average concentration killing 50% of cells, 22 microgram/ml; range, 2.8 to 65.4). Cells derived from catecholamine-producing tumors were more sensitive to 6-OHDA than were those from non-catecholamine producers. By contrast, human fibroblasts, lymphoblastoid cell lines, and normal marrow were relatively insensitive to 6-OHDA; the concentration needed to kill 50% of cells for most of these cells exceeded 100 microgram/ml. Leukemia cell lines and a rhabdomyosarcoma cell line were intermediate in sensitivity. Ascorbate and 6-OHDA were synergistic in toxicity for human neuroblastoma cells. Thus, in vitro addition of 6-OHDA and ascorbate was rapidly lethal for human neuroblastoma cells at concentrations which were minimally toxic for hematopoietic cells. This differential toxicity provides a possible means for selective destruction of neuroblastoma cells in bone marrow harvested for autologous transplantation.

Pharmacology and toxicity of intracarotid adriamycin administration following osmotic blood-brain barrier modification.

The effect of reversible blood-brain barrier modification on the delivery of Adriamycin to the brain was studied in a rodent and canine model. Pharmacokinetic and physiological studies were done in these animals after a wide range of doses of Adriamycin (0.1 to 1.0 mg/kg) were administered into the carotid artery following osmotic barrier modification with mannitol. In the absence of barrier modification, no immunoreactive Adriamycin was detected in the cerebrum; whereas, following barrier modification, up to 4.5 micrograms of drug and/or metabolites per g of brain were found. Optimum tissue levels of Adriamycin and metabolites were achieved following barrier modification when the drug was administered by either bolus or slow continuous (15-min) infusion. Immunoreactive drug was identified in brain for up to 6 hr after administration. Significant functional neurotoxicity occurred at all dose levels, even at 0.1 mg/kg, a level at which Adriamycin concentration in the brain was below the level of detectability. Neuropathological examination revealed the presence of necrosis and hemorrhagic infarcts. Thus, these pharmacological and toxicity studies suggest that Adriamycin (or its metabolites) may produce significant clinical neurotoxicity when even small amounts penetrate the blood-brain barrier.

Growth of human lung tumor in the brain of the nude rat as a model to evaluate antitumor agent delivery across the blood-brain barrier.

We have developed a brain tumor model in the nude rat utilizing NCI-N417D human small cell carcinoma of the lung grown both intracerebrally and s.c. The median latency period from the time of intracerebral tumor inoculation to the onset of neurological symptoms is 13 days with an intracerebral tumor take rate of 91% (29 of 32). The median survival is 13 days, and all animals were dead by Day 26. The tumor is discrete, well circumscribed, with occasional leptomeningeal spread and with minimal evidence of surrounding cerebral edema. Intracerebrally, this tumor is usually impermeable to Evan's blue:albumin (Mr 68,500) but not fluorescein (Mr 376). Although variable, the intracerebral tumor is less permeable to methotrexate than is the same tumor grown s.c. in the same animal (P less than 0.005). The intraarterial and i.v. routes of methotrexate administration in the presence and absence of blood-brain barrier opening were evaluated. Drug delivery to the intracerebral tumor and ipsilateral brain was significantly (P less than 0.025) greater when the methotrexate was given intraarterially and was significantly (P less than 0.0025) increased after osmotic blood-brain barrier opening. After barrier opening, methotrexate concentration was enhanced 3- to 4-fold in tumor and 10- to 20-fold in brain around tumor. Thus, the nude rat provides a model to investigate the biology and therapeutic responsiveness of human small cell carcinoma of the lung grown intracerebrally where it develops a blood-tumor barrier similar to that seen in humans. This model further provides the unique opportunity to investigate the role of osmotic blood-brain barrier opening in the treatment of a tumor which is sensitive to chemotherapeutic agents and for which tumor-specific monoclonal antibodies are available.

Synergy between methionine stress and chemotherapy in the treatment of brain tumor xenografts in athymic mice.

This study describes a novel approach to the treatment of brain tumors with the combination of recombinant L-methionine-alpha-deamino-gamma-lyase and chemotherapeutic regimens that are currently used against such tumors. The growth of Daoy, SWB77, and D-54 xenografts in athymic mice was arrested after the depletion of mouse plasma methionine (MET) with a combination of a MET- and choline-free diet and recombinant L-methionine-alpha-deamino-gamma-lyase. The treated tumor-bearing mice were rescued from the toxic effects of MET withdrawal with daily i.p. homocystine. This regimen suppressed plasma MET to levels below 5 microM for several days, with no treatment-related deaths. MET depletion for 10-12 days induced mitotic and cell cycle arrest, apoptotic death, and widespread necrosis in tumors but did not prevent tumor regrowth after cessation of the regimen. However, when a single dose of 35 mg/m(2) of N,N'-bis(2-chloroethyl)-N-nitrosourea (BCNU), which was otherwise ineffective as a single therapy in any of the tumors tested, was given at the end of the MET depletion regimen, a more than 80-day growth delay was observed for Daoy and D-54, whereas the growth of SWB77 was delayed by 20 days. MET-depleting regimens also trebled the efficacy of temozolomide (TMZ) against SWB77 when TMZ was given to animals as a single dose of 180 mg/m(2) at the end of a 10-day period of MET depletion. The enhanced responses of both Daoy and SWB77 to DNA alkylating agents such as BCNU and TMZ could be attributed to the down-regulation of O(6)-methylguanine-DNA methyltransferase activity. However, the synergy of MET depletion and BCNU observed with D-54 tumors, which do not express measurable O(6)-methylguanine-DNA methyltransferase protein, is probably mediated by a different mechanism. MET depletion specifically sensitizes tumors to alkylating agents and does not significantly lower the toxicity of either BCNU or TMZ for the host. In this regard, the combination approach of MET depletion and genotoxic chemotherapy demonstrates significant promise for clinical evaluation.

Effect of vitamin B-12 deficiency on the hepatic tissue concentration of acyl carnitines.

Concentrations of carnitine, acetyl carnitine, propionyl carnitine, and long chain acyl carnitines have been measured in hepatic tissue of normal and vitamin B-12 deficient rats using radiolabelled butyrobetaine to label carnitine pools. Increased levels of propionyl carnitine were seen in the livers of vitamin B-12 deprived animals when compared to those from normal animals. Methylmalonyl carnitine was not detected in the B-12 deprived animals. Free carnitine levels were no different in the livers from the B-12 deprived animals than from the normal control animals.

Large cell lymphomas of the stomach: improved prognosis with complete resection of all intrinsic gastrointestinal disease.

Thirty-seven consecutive patients with large cell lymphoma involving the stomach were evaluated between 1974 and 1980. All seven stage IE patients underwent complete resection of the stomach and all patients are alive 21-41 mo after resection. Of 18 stage IIE, 11 underwent complete resection. Two resected patients without postoperative therapy died of their disease. Six patients treated with chemotherapy are alive and well, and two of three patients treated with radiotherapy remain alive without disease. Seven patients had incomplete resection or biopsy, and only one remains alive at 34 mo. Of eight stage IV patients, four had complete resection and chemotherapy without recurrence of their disease. All four patients who were not resected have died of their disease. This study strongly supports the role of early surgery in the management of gastric large cell lymphomas.

The relative value of conventional staging procedures for developing prognostic models in extensive-stage small-cell lung cancer.

Published prognostic models for small-cell lung cancer (SCLC) have either combined limited- and extensive-stage patients or have not included standard anatomic staging information to assess the relative value of the knowledge of specific sites and number of sites of metastases in predicting survival in extensive-stage disease. We studied 136 extensive-stage patients in whom traditional staging procedures were performed and in whom other previously demonstrated significant pretreatment variables were determined. Using the Cox proportional hazards model, when all data were included, three variables were significant: performance status (PS) (P = .0001), number of sites of metastases (P = .0010), and age (P = .0029). A prognostic algorithm was developed using these variables, which divided the patients into three distinct groups. When the anatomic staging data were omitted, the serum albumin (P = .0313) was the only variable in addition to PS (P = .0001) and age (P = .0064) that was significant. An alternative algorithm using these three variables was nearly as predictive as the original. Therefore, in extensive-stage patients, reasonable pretreatment prognostic information can be obtained without using the number or specific sites of metastases as variables once the presence of distant metastases has been demonstrated.

Phase I study of paclitaxel given by seven-week continuous infusion concurrent with radiation therapy for locally advanced squamous cell carcinoma of the head and neck.

PURPOSE: Paclitaxel is one of the most active agents for squamous cell carcinoma of the head and neck (SCCHN) and an in vitro radiosensitizer. The dose-response relationship for paclitaxel may depend more on exposure duration than on peak concentration. This National Cancer Institute-sponsored phase I trial was designed to determine the feasibility of combining continuous-infusion (CI) paclitaxel with concurrent radiation therapy (RT). PATIENTS AND METHODS: Patients with previously untreated stage IVA/B SCCHN were eligible. Primary end points were determination of the maximum-tolerated dose, dose-limiting toxicity, and pharmacokinetics for paclitaxel given by CI (24 hours a day, 7 days a week for 7 weeks) during RT (70 Gy/7 weeks). RESULTS: Twenty-seven patients were enrolled and assessable for toxicity. Nineteen of the patients who completed > or = 70 Gy were assessable for response. Grade 3 skin and mucosal acute reactions occurred at 10.5 mg/m(2)/d, but uninterrupted treatment was possible in five of six patients. At 17 mg/m(2)/d, skin toxicity required a 2-week treatment break for all three patients. The mean paclitaxel serum concentration at dose levels > or = 6.5 mg/m(2)/d exceeded that reported to achieve in vitro radiosensitization. Initial locoregional control was achieved in 14 (58%) of 24 of patients treated to 70 Gy, and control persisted in nine (38%). CONCLUSION: CI paclitaxel with concurrent RT is a feasible and tolerable regimen for patients with advanced SCCHN and good performance status. Preliminary response and survival data are encouraging and suggest that further study is indicated. The recommended phase II dose of paclitaxel by CI is 10.5 mg/m(2)/d with RT for SCCHN.

A phase I single-dose trial of gadolinium texaphyrin (Gd-Tex), a tumor selective radiation sensitizer detectable by magnetic resonance imaging.

Gadolinium Texaphyrin (Gd-Tex) is a radiation sensitizer with a novel mechanism of action that sensitizes both oxic and hypoxic cells, localizes selectively in tumors, and is detectable by magnetic resonance imaging (MRI). This Phase I single-dose trial of Gd-Tex administered concurrently with radiation therapy was carried out to determine the maximally tolerated dose (MTD), dose-limiting toxicities, pharmacokinetics, and biolocalization of Gd-Tex as determined by MRI. Adults with incurable cancers of any histology requiring radiation therapy were eligible. A single i.v. dose of Gd-Tex was followed at least 2 h later by radiation therapy. The Gd-Tex dose was escalated in cohorts of 3 to 5 patients. Thirty-eight patients (median age, 58 years; range, 35-77 years) with incurable cancers of the lung (26), cervix (3), or other solid tumors (9) received a total of 41 single administrations of Gd-Tex. The Gd-Tex dose was escalated from 0.6 to 29.6 mg/kg. Irradiated sites included the thorax, brain, pelvis, bone, soft tissue, and sites of nodal metastases. The MTD was 22.3 mg/kg, determined by reversible acute tubular necrosis as the dose-limiting toxicities. Gd-Tex selectively accumulated in primary and metastatic tumors as demonstrated by MRI. No increase in radiation toxicity to normal tissues was seen. The median half-life of Gd-Tex after single-dose administration is 7.4 h. This study demonstrates that Gd-Tex is well tolerated in doses below the MTD, and that there is selective biolocalization in tumors. The maximum recommended dose for single administrations is 16.7 mg/kg.

Risk of alloimmunization and delayed hemolytic transfusion reactions in patients with sickle cell disease.

Blood transfusion is an integral part of the supportive care of patients with sickle cell diseases. The hazards of red blood cell alloimmunization and delayed hemolytic transfusion reactions (DHTRs) complicate the treatment of patients with sickle cell diseases, particularly since such reactions may be misinterpreted as a pain crisis, and, as a result, specific transfusion serologic studies may not be performed. The frequency of alloimmunization in this population has been the subject of several reports; however, the frequency of DHTRs is unknown. To determine the frequency of this event, we retrospectively reviewed the medical and transfusion service records of all adult patients with sickle cell diseases transfused during the six-year period from January 1980 to December 1985. Seventy-three adult patients with sickle cell diseases received transfusions. The prevalence of recognized DHTR was three (4%) of 73. Red blood cell alloimmunization was seen in 22 (30%) of 73 of the patients. The calculated risk of alloimmunization was 3.1% per unit of blood. These observations suggest that alloimmunization and clinically apparent DHTRs occur more frequently in patients with sickle cell diseases and support pretransfusion testing for at least Rh and Kell red blood cell antigens in patients who are at high risk of such events (patients who have formed an alloantibody or who are being enrolled in a transfusion program).

Training and practice activities of hematology and medical oncology diplomates.

Diplomates of the American Board of Internal Medicine in hematology or medical oncology were surveyed about the content and setting of their practices, adequacy of training for professional activities, and preferences for certification. The response rate was 60% (N = 2516). Approximately 20% of cases seen by diplomates in hematology involve nonhematopoietic neoplasms, and 10% of cases managed by oncologists concern hematologic disorders. Diplomates were satisfied with training in areas corresponding to their own field(s) of certification, except for immune and/or acquired immunodeficiency syndrome-related and nonneoplastic leukocyte disorders. Training deficits most frequently recalled were office management skills and psychosocial/communication skills. Nearly half of the respondents preferred to maintain separate certificates. Data indicate that the two fields are distinct. However, the overlap in practice brings into question the adequacy of training for diplomates who manage problems outside of their field of certification and suggests that some degree of cross-fertilization in all training would be beneficial.

Lack of effect of riboflavin deficiency on vitamin B12-related metabolic pathways and fatty acid synthesis.

The neurological sequelae of riboflavin deficiency posed the possibility that this tissue injury was mediated by defective vitamin B12 function due to the requirement for riboflavin-dependent oxidoreductase systems in B12 coenzyme synthesis and function. Studies of the B12-dependent enzymatic reactions (5-methyltetrahydrofolic-homocysteine methyltransferase and methylmalonyl coenzyme A mutase) in a fiboflavin-deficient rat model documented normal B12 activity in liver and neural tissue. In addition, examination of neural lipids and separation and analysis of neural fatty acids failed to reveal the increased odd chain fatty acids characteristically seen in the B12-deficient state. Thus, the neural tissue sequelae of riboflavin deficiency do not appear to relate to B12 coenzyme function.